1.2千巴围压下岩样破裂和摩擦滑动过程中电阻率变化h
ELECTRICAL RESISTIVITY CHANGES IN ROCK SAMPLES DURING FRACTURE AND FRICTIONAL SLIDING AT 1.2 KB CONFINE PRESSURE
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摘要: 在1.2千巴围压下进行了三种初始饱和岩样(辉长岩、花岗岩Ⅰ和Ⅱ,各以淡水和盐水饱和)的压缩实验直至破裂并继续到摩擦滑动,所有实验中测定了岩样电阻率。 以Brace等人研究表面电导的方法为基础,我们引入给定含水岩样的体电阻系数和面电导系数两个专用术语以分析实验结果。发现一旦岩样开始膨胀,其面电导系数随差应力增加都增大。结果表明:含水岩样体膨胀后电阻率下降主要是由于表面电导作用的增强。 和前人的结果不同,不同岩样摩擦滑动时电阻率变化各异。作者提出:这种差异可能与岩石中所含矿物颗粒大小有关。含大颗粒的岩石滑动时电阻率下降,而含小颗粒的岩石滑动时电阻率上升。Abstract: Axial compressive experiments were carried out up to fracture and extended to frictional sliding for three types of initially water-saturated cylindrical rock samples (gabbro,graniteⅠ and Ⅱsaturated with tap water or salt water respectively) at 1.2kb confine pressure. Electrical resistivities of rock samples were measured during all these experiments.On the basis of Brace's method of investigating surface conduction,we analysed the experimental results by introducing two special terms namely the volume resistance coefficient and the surface conduction coefficient for a given wet rock sample. We found that all surface conduction coefficient increased wfth deviatoric stress as soon as the rock sample began to dilate. It was proved that resistivities in wet rock 'samples decrease after dilatancy mainly because of the increase of the surface conductivity.In contrast to previous work,the resistivity of various rock samples changed in different ways during frictional sliding. It is proposed in this paper that this difference may be related to the size of grains in the rocks. The resistivity of rock sample containing coarser grains decreases whereas that of rock sample containig finer grains increases during sliding.
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[1] Brace, W. F., A. S. Orange, and T. M. Madden, The effect of pressure on the electrical resistivity
[2] Rai, C. S., and M. H. Manghnani, The effect of saturant salinity and pressure on the electrical resistivity of Hawaiian basalts, Geophys.R. Astr. Soc. 65, 395——405, 1981.
[3] Brace, W. F,and A. S. Orange, Electrical resistivity change in saturated rocks during fracture and frictional sliding,].Geophys. Res., 73(4), 1433——1445, 1968.
[4] Brace, W. F., Dilatancy——related electrical resistivity changes in rocks, Pure Appl. Geophys., 113,207——217, 1975.
[5] 陈颊、姚孝新、耿乃光,应力途径、岩石的强度和体积膨胀,中国科学,11, 1093——1100, 1979,
[6] Wang, C. Y,R. E. Goodman, P. N. Sundaram and H. F. Morrison, Electrical resistivity of granite in frictional sliding: application to earthquake prediction, Geophys. Res. Let., 2, 525——528, 1975.
[7] Wang, C. Y., P. N. Sundaram and R. E. Goodman, Electrical resistivity changes in rock during frictional sliding and fracture, Pure Appl. Geophys., 116, 4/5, 717——731, 1978.[1] Brace, W. F., A. S. Orange, and T. M. Madden, The effect of pressure on the electrical resistivity
[2] Rai, C. S., and M. H. Manghnani, The effect of saturant salinity and pressure on the electrical resistivity of Hawaiian basalts, Geophys.R. Astr. Soc. 65, 395——405, 1981.
[3] Brace, W. F,and A. S. Orange, Electrical resistivity change in saturated rocks during fracture and frictional sliding,].Geophys. Res., 73(4), 1433——1445, 1968.
[4] Brace, W. F., Dilatancy——related electrical resistivity changes in rocks, Pure Appl. Geophys., 113,207——217, 1975.
[5] 陈颊、姚孝新、耿乃光,应力途径、岩石的强度和体积膨胀,中国科学,11, 1093——1100, 1979,
[6] Wang, C. Y,R. E. Goodman, P. N. Sundaram and H. F. Morrison, Electrical resistivity of granite in frictional sliding: application to earthquake prediction, Geophys. Res. Let., 2, 525——528, 1975.
[7] Wang, C. Y., P. N. Sundaram and R. E. Goodman, Electrical resistivity changes in rock during frictional sliding and fracture, Pure Appl. Geophys., 116, 4/5, 717——731, 1978.
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